1. Field of the Invention
The present invention relates to a method of and an apparatus for generating an image exchanged between a laboratory and a customer in a digital input output service for photographs such that an image having been output digitally at a laboratory and provided to a customer is later brought in to the laboratory again to be output as a print.
2. Description of the Related Art
A digital output service is known for recording image data read from a developed film or the like in a recording medium such as a CD-R, an MO disc, or the like, and for providing the recording medium to a customer. Also known is a digital input service in which a customer uses a personal computer to process image data that has been output by the digital output service and in which the customer brings the processed data to a laboratory to be reproduced as a photographic print.
A color space (a color coordinate system) for representing a digital image generally depends on equipment for handling the digital image. In other words, a system in a laboratory manages an image in a color coordinate system appropriate for dealing with the image to be output as a print. A personal computer manages an image in a color coordinate system such that the image can be displayed esthetically when displayed on a CRT. Therefore, using the above digital input output service, a conversion from a color space that is specific to a laboratory system (hereinafter called a specific color space) to a color space that is standard for a personal computer (hereinafter called a standard color space) is generally carried out when an image is output. Furthermore, when this image is input again into the system in the laboratory to be output as a print, a conversion from the standard color space to the specific color space is reversely carried out.
Since the values of pixels in an image are stored as data in a predetermined bit depth, the values that the pixels can take are restricted by the bit depth. For example, if 8-bit data are used, the values that the pixels can take are limited to integers from 0 to 255. However, the values which are obtained after the color space conversion on the digital image are not necessarily limited to the numbers in the same range, and adjustments such as a replacement of a negative value with 0 or a replacement of a number greater than 255 with 255 are carried out upon the conversion. It is therefore not guaranteed that an image which has once been converted to the standard color space will be restored completely after an inversion to the specific color space, and restoration errors may be created. This is one of the causes of print quality degradation.